WASHINGTON – The Treasury Department says it has uncovered evidence that Iran has been stealthily using passenger and cargo aircraft to assist Syria President Bashar al-Assad’s bloody crackdown in recent months.

According to department documents, Iran Air and Mahan Air used flights between Tehran and Damascus during the summer to provide weapons and crowd control equipment as thousands were slaughtered.

Crucial evidence U.S. intelligence agents have obtained from U.S. allies indicates the practice is not a new development.

“A Turkish inspection in March 2011 of a Yas Air flight bound for Syria, which listed ‘auto spare parts’ on its cargo manifest, found weapons including Kalashnikov AK-47 assault rifles, machine guns, nearly 8,000 rounds of ammunition, as well as an assortment of mortar shells,” says a statement from the Treasury.

The Treasury, as a result, has added 117 aircraft operated by Iran Air, Mahan Air, and Yas Air to the Office of Foreign Assets Control (OFAC) Specially Designated Nationals (SDN) List.

Sanctions will be applied against the operators of those airlines, making it difficult for them to do business and increasing the tension the Iranian government is under because of its nuclear weapons program.

Treasury Under Secretary for Terrorism and Financial Intelligence David S. Cohen says in a statement that the sanctions “seek to disrupt the flow of weapons and communications equipment to the Syrian regime and help prevent their use against the Syrian people.”

The assertion is that Iran, with the help of Hezbollah and the Islamic Revolutionary Guard Corps, has assisted the Syrian government in an overpowering show of force that has claimed more than 20,000 lives.

Any kind of assistance to the Syrian regime was deemed illegal by Presidential Executive Order 13582, “Blocking Property of the Government of Syria and Prohibiting Certain Transactions with Respect to Syria.”

The Treasury says Iran has employed deceptive measures when shipping prohibited items to Syria, by using a combination of passenger and cargo flights and declaring illicit cargo as humanitarian or otherwise legitimate goods.

In the case of Yas Air, the Iranian cargo airline allegedly has moved the Revolutionary Guard’s Quds Force personnel and weapons under the cover of humanitarian aid.

Iran Air also was caught on June 23, 2011 providing support and services to Iran’s Aerospace Industries Organization and the Revolutionary Guard, which are tied to Iran’s ballistic missile program.

Iran is banned from engaging in any activity related to developing a nuclear weapon or a delivery system.

The Office of Foreign Assets Control says “on numerous occasions since 2000, Iran Air has shipped military-related equipment on behalf of MODAFL and IRGC.”

Iranian President Mahmoud Ahmadinejad, who delivered a speech at the United Nation’s General Assembly meeting in New York Tuesday, did not mention Iran’s nuclear program at all, or the new sanctions.